1. Field to which the Invention Relates
The invention relates to an industrial robot with a boom having a clasping member at its front end, which is engaged by two levers, of which one lever is connected via rotary joints with the boom and also with the base plate carrying the boom and the levers.
2. The Prior Art
A known industrial robot is described, for example, in the German patent (Auslegeschrift) No. 2,226,407. Industrial robots of this type of construction have a clasping member arranged on a boom. With this clasping member it is possible to carry out manipulations as for example assembly, welding, drilling, transporting and also loading and unloading.
These manipulations should be capable of being carried out as precisely as possible. The robot is driven by electric motors and in its field of operation it should be possible to reach any desired point precisely. Furthermore the robot should be capable of being aligned in accordance with six coordinates at the most, that is to say in accordance with three basic coordinates, which define movement towards the point in space, and in accordance with three clasping member coordinates, which define the alignment of the workpiece or tool at this point. The three basic coordinates are constituted by the vertical axis of rotation of the robot, a horizontal axis for horizontal movements and the vertical axis for vertical movements. Furthermore for such a robot it is necessary to make provisions to enable it to move substantial loads.
In the case of the German Pat. No. 2,226,407 the robot described has a first lever which can be rotated about a horizontal axis on the support plate. The other end of this lever is connected via a horizontal shaft with the rear end of the boom. On this lever a further lever is pivotally mounted via a horizontal shaft, which has its other end connected with the boom via a longitudinal guide. The piston rod of a cylinder makes engagement with its other lever on which the weight of the boom acts and which accordingly is to bring about weight equalization.
The point or curve control system in the known assembly is extremely complicated, since the front boom end, on which the clasping member is arranged, necessarily carries out curved movements. If for example a movement in the direction of the horizontal axis is to be carried out, it is then only possible to carry out a horizontal movement to the front or the rear of the front boom end if simultaneously the vertical movement, due to the unavoidable curve movement, of the front boom end is equalized by the use of an electric motor. As a result the control program becomes extremely complicated. Furthermore it is disadvantageous that the boom weight, that is to say the weight carried by the clasping member, cannot be automatically equalized, for example using the principle of a weighing beam.
Furthermore other industrial robots have been proposed, which however possess at least one of the above mentioned disadvantages. Frequently the speed and power factors in such robots are so unsuitable that reliable positioning is not possible.